Perpendicular magnetic recording medium and magnetic storage apparatus using the same

Abstract

Embodiments in accordance with the present invention help to obtain a perpendicular magnetic recording medium having a granular structure, excellent recording/reproducing properties, and excellent durability. According to one embodiment, a recording layer includes a layer which has crystal grains mainly composed of cobalt and crystal grain boundaries mainly composed of the oxide; the oxygen content of the recoding layer is changed in the film thickness direction; the oxygen content in the area in the vicinity of the interface between the recording layer and the intermediate layer is made lower than the oxygen content in the area in the vicinity of the center of the recording layer; and the oxygen content in the area in the vicinity of the interface between the recording layer and the protective layer is made lower than the oxygen content in the area in the vicinity of the center of the recording layer.

1. A perpendicular magnetic recording medium comprising: an underlayer, an intermediate layer, a recording layer, and a protective layer, deposited, in order over a substrate,
 wherein the recording layer includes a layer which consists of crystal grains mainly composed of cobalt and crystal grain boundaries mainly composed of an oxide, 
 wherein an oxygen content of the recording layer changes along the film thickness direction, the oxygen content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is lower than the oxygen content of an area of about 4 nm in the vicinity of the center of the recording layer, and the oxygen content in an area of 4 nm from the interface between the recording layer and the protective layer is lower than 5 at % and lower than the oxygen content in the area of about 4 nm in the vicinity of the center of the recording layer, and 
 wherein the recording layer contains chromium, 
 a mean chromium content in the recording layer changes along the film thickness direction, and 
 the mean chromium content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is higher than the mean chromium content in an area of about 4 nm in the vicinity of the center of the recording layer. 
 
     
     
       2. A perpendicular magnetic recording medium comprising:
 an underlayer, an intermediate layer, a recording layer, and a protective layer, deposited, in order, over a substrate, 
 wherein the recording layer includes a layer which consists of crystal grains mainly composed of cobalt and crystal grain boundaries mainly composed of an oxide, and 
 wherein, in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer, an oxygen content increases from the interface with the intermediate layer to the protective layer side and, in an area of from the interface between the recording layer and the protective layer, the oxygen content is lower than 5 at % and increases from the interface with the protective layer to the intermediate layer side, and 
 wherein the recording layer contains chromium, 
 a mean chromium content in the recording layer changes along the film thickness direction, and 
 the mean chromium content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is higher than the mean chromium content in an area of about 4 nm in the vicinity of the center of the recording layer. 
 
     
     
       3. The perpendicular magnetic recording medium according to  claim 1 , wherein
 the intermediate layer includes a layer which is formed adjacent to the recording layer and consists of crystal grains mainly composed of ruthenium and crystal grain boundaries mainly composed of the oxide. 
 
     
     
       4. The perpendicular magnetic recording medium according to  claim 1 , wherein
 the recording layer contains platinum and the platinum content of the recording layer changes along the film thickness direction, 
 the platinum content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is lower than the platinum content in an area of about 4 nm in the vicinity of the center of the recording layer, and 
 a non-magnetic layer is formed between the area in the vicinity of interface of the recording layer and the intermediate layer and the area in the vicinity of center of the recording layer. 
 
     
     
       5. The perpendicular magnetic recording medium according to  claim 1 , wherein
 the recording layer has a discontinuous structure periodically delimited in a film plane. 
 
     
     
       6. The perpendicular magnetic recording medium according to  claim 2 , wherein
 the intermediate layer includes a layer which is formed adjacent to the recording layer and consists of crystal grains mainly composed of ruthenium and crystal grain boundaries mainly composed of the oxide. 
 
     
     
       7. The perpendicular magnetic recording medium according to  claim 2 , wherein
 the recording layer contains platinum and the platinum content of the recording layer changes along the film thickness direction, 
 the platinum content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is lower than the platinum content in an area of about 4 nm in the vicinity of the center of the recording layer, and 
 a non-magnetic layer is formed between the area in the vicinity of interface of the recording layer and the intermediate layer and the area in the vicinity of center of the recording layer. 
 
     
     
       8. The perpendicular magnetic recording medium according to  claim 2 , wherein the recording layer has a discrete structure periodically delimited in a film plane. 
     
     
       9. A magnetic storage apparatus comprising:
 a magnetic recording medium; 
 a means for driving the magnetic recording medium in a recording direction; 
 a magnetic head including a recording unit and a read element; 
 a means to drive the magnetic head relative to a perpendicular magnetic recording medium; and 
 a signal processing unit to process input signals and output signals to and from the magnetic head, 
 wherein the magnetic recording medium includes a substrate on which an underlayer, an intermediate layer, a recording layer, and a protective layer are deposited, in order, the recording layer includes a layer consisting of crystal grains mainly composed of cobalt and crystal grain boundaries mainly composed of an oxide, and 
 wherein an oxygen content of the recording layer changes along the film thickness direction, the oxygen content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is lower than the oxygen content of an area of about 4 nm in the vicinity of the center of the recording layer, and the oxygen content in an area of 4 nm from the interface between the recording layer and the protective layer is lower than 5 at % and lower than the oxygen content of the area of about 4 nm in the vicinity of the center of the recording layer, and 
 wherein the recording layer contains chromium, 
 the mean chromium content in the recording layer changes along the film thickness direction, and 
 the mean chromium content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is higher than the mean chromium content in an area of about 4 nm in the vicinity of the center of the recording layer. 
 
     
     
       10. The magnetic storage apparatus according to  claim 9 , wherein the intermediate layer includes a layer which is formed adjacent to the recording layer and consists of crystal grains mainly composed of ruthenium and crystal grain boundaries mainly composed of the oxide. 
     
     
       11. The magnetic storage apparatus according to  claim 9 , wherein
 the recording layer contains platinum and a platinum content of the recording layer changes along the film thickness direction, 
 the platinum content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is lower than the platinum content in an area of about 4 nm in the vicinity of the center of the recording layer, and 
 a non-magnetic layer is formed between the area in the vicinity of interface of the recording layer and the intermediate layer and the area in the vicinity of center of the recording layer. 
 
     
     
       12. A magnetic storage apparatus according to  claim 9 , wherein
 the recording layer has a discontinuous structure periodically delimited in the film plane. 
 
     
     
       13. A magnetic storage apparatus comprising:
 a magnetic recording medium; 
 a means for driving the magnetic recording medium in the recording direction; 
 a magnetic head including a recording unit and a reading element; 
 a means to drive the magnetic head relative to the magnetic recording medium; and 
 a signal processing unit to process input signals and output signals to and from the magnetic head, 
 wherein the magnetic recording medium includes a substrate on which an underlayer, an intermediate layer, a recording layer, and a protective layer are deposited, in order, and the recording layer includes a layer consisting of crystal grains mainly composed of cobalt and crystal grain boundaries mainly composed of an oxide, and 
 wherein, in an area of about 4 nm in the vicinity of the interface between the recording layer to the intermediate layer, an oxygen content increases from the interface with the intermediate layer to the protective layer side, and in area of from the interface between the recording layer and the protective layer, the oxygen content is lower than 5 at % and increases from the interface with the protective layer to the intermediate layer side, and 
 wherein 
 the recording layer contains chromium, 
 the mean chromium content in the recording layer changes along the film thickness direction, and 
 the mean chromium content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is higher than the mean chromium content in an area of about 4 nm in the vicinity of the center of the recording layer. 
 
     
     
       14. The magnetic storage apparatus according to  claim 13 , wherein the intermediate layer includes a layer which is formed adjacent to the recording layer and consists of crystal grains mainly composed of ruthenium and crystal grain boundaries mainly composed of the oxide. 
     
     
       15. The magnetic storage apparatus according to  claim 13 , wherein
 the recording layer contains platinum and the platinum content of the recording layer changes along the film thickness direction, 
 the platinum content in an area of about 4 nm in the vicinity of the interface between the recording layer and the intermediate layer is lower than the platinum content in an area of about 4 nm in the vicinity of the center of the recording layer, and 
 a non-magnetic layer is formed between the area in the vicinity of interface of the recording layer and the intermediate layer and the area in the vicinity of center of the recording layer. 
 
     
     
       16. A magnetic storage apparatus according to  claim 13 , wherein the recording layer has a discontinuous structure periodically delimited in a film plane.